Atekomi (アテコミ)is a play aiming to cut a diagonal play (kosumi). That is, it creates a cutting point from the opponent's diagonal.
So here is atekomi (something like "aim inside").
There are some cases where atekomi is a hard-to-find tesuji. Normally of course White can simply connect as an answer, so such cases must depend on some factor like shortage of liberties, or the creation of two cutting points at once.
See for example blind spot, example 1.
is atekomi. Black can't protect at both a and b.
- Hu
See also warikomi tesuji.